Partial conversion to use of useSyncExternalStore

[mrclay]

What is the purpose of this pull request? (put an "X" next to item)

[ ] Documentation update [ ] Bug fix [ ] New feature [ ] Other, please explain:

What changes did you make? (Give an overview)

Which issue (if any) does this pull request address?

Is there anything you'd like reviewers to focus on?

[aralroca]

Hey @mrclay , about this PR we saw that is currently in Draft but looks like that is already done and all tests pass. It's ready to review to merge?

[mrclay]

I seem to recall several tests not working for me locally, so I'm not at all confident that it's ready.